DC-10-10CF (9 built): Convertible passenger/cargo transport aircraft. Only built for Continental Airlines(8) and United Airlines (1) DC-10-15 (7 built): Also known as the "DC-10 Sport", designed for use at hot high-altitude airports. The series 15 was fitted with higher-thrust GE CF6-50 powerplants. Only built for Mexican carriers Aeromexico and Mexicana. Produced between 1979 and 1982 DC-10-20 DC-10-30 (164 built): The most common model, built with General Electric CF6-50 turbofan engines and larger fuel tanks to increase range and fuel efficiency, as well as a set of rear center landing gears to support the increased weight. It was the second long-range model after the -40 and very popular with European flag carriers. Produced from 1972 to 1988, the DC-10-30 was delivered to 38 different customers, amongst which Lufthansa (11), Swissair (11), VARIG(11), KLM (10) and Iberia(9) were the largest. DC-10-30ER (6 built) DC-10-30F (10 Built) DC-10-40 (42 built) KC-10A-Extender (60 built): Military version of the DC-10-30 used for air to air refulling. The aircraft was ordered by the U.S. Air Force. Produced from 1981. It is the longest-ranged production aircraft in the world. KDC-10 (4 built): Aerial refueling tanker for the Royal Netherlands Airlines. Converted from civil airliners (DC-10-30CF) to a similar standard as the KC-10.